Implantable medical devices that provide therapy such as electrical stimulation or drug delivery, are programmed to utilize a special mode just prior to the patient having the implantable medical device undergoing a particular procedure such as a magnetic resonance imaging (MRI) scan. In the case of an MRI, the special mode, referred to herein as an MRI mode, for an implantable medical device that provides stimulation therapy may alter the normal stimulation by utilizing an asynchronous form of pacing that avoids triggering or inhibiting pacing as a function of sensing. The MRI mode avoids the various fields of the MRI machine, including static and time varying magnetic fields as well as radio frequency electromagnetic waves, from causing false sensing of intrinsic signals like intrinsic heartbeats which can lead to improper pacing. As another example, MRI mode in a drug delivery device may better protect the on-board supplies. Furthermore, MRI mode may disconnect a telemetry antenna for some implantable medical devices.
One issue in particular may occur during an MRI scan while the implantable medical device operates in the MRI mode. The fields of the MRI scan may trigger the implantable medical device to experience a device reset, also known as a power on reset. The device reset may impact the operation of the implantable medical device to varying degrees depending upon the severity of the reset. In some cases, the reset may not impact the continued operation of the implantable medical device in the MRI mode because the volatile memory where the programming is stored is not erased. However, in cases where the device reset does erase the programming from the volatile memory, the implantable medical device defaults to a non-MRI mode which is intended for device recovery in non-MRI contexts. This non-MRI mode that is recovered is typically less optimized for operation in the MRI context. This is especially true for implantable cardiac defibrillators that often recover in a non-MRI mode that does not perform pacing and has tachyarrhythmia detection and therapies enabled. As a result, the patient and/or the implantable medical device may be at a greater risk after the device reset.